Intermodal containers are an efficient way to transport large amounts of containerized cargo. Modern commerce relies on efficient transportation of intermodal containers. Due to the nature and transportability of intermodal containers, individuals may attempt to introduce items such as toxic chemicals, illegal or unauthorized substances such as narcotics, and radioactive/fissionable materials to avoid detection in transport.
There are two methods for screening intermodal containers, the Lay Down Method and the TraPack Method. The Lay Down Method uses a vehicle mounted scanner to screen containers and the Trapack Method involves positioning an intermodal container on a rail system to effectuate scanning. In the TraPack method, a straddle carrier sets the intermodal container on the rail system and picks it up again once scanning is complete. A straddle carrier is a vehicle with a frame structure having a lift mechanism capable of picking up an intermodal container. Most straddle carriers are powered by an internal combustion engine, e.g., a diesel engine but new hybrid units are now becoming available.
In the Lay Down Method, a straddle carrier lays down an intermodal container for screening. The container is screened by driving a truck with a scanner mounted on an arm past the container. The scanner evaluates the container's contents for radioactivity. Once complete, the straddle carrier picks up the container for further transport or storage.
In the TraPack Method a straddle carrier to picks up the intermodal container and places it on a rail type mechanism, e.g., a conveyor belt. The container is sent through a radiation scanner by moving it on the rails. After scanning, the rail mechanism moves it out of the scanner into a position for pick up by the straddle carrier for storage or transport.